in response, top officials in the obama administration argued their actions are justified and legal. >> primary concern is to keep the american people safe, now do so in a way that's consistent with our laws and our values. >> ifill: attorney general eric holder today defended the justice department's rationale for authorizing the killings of americans overseas. >> we are -- we have as a basis for action that we take a congressional statute that allows us to operate against al qaeda and associated entities not only in pakistan or not only in afghanistan but in other parts of the world. we say that we only take these kinds of actions when there's an imminent threat, when capture is not feasible and when we are confident that we're doing so in a they's consistent with a federal international law. >> ifill: nbc news obtained a 16-page justice department white paper apparently prepared for congressional committees last summer that describes the obama administration's legal reasoning the document said a lethal operation is legal if it targets a senior operational leader of al qaeda or an